In some situations, and particularly in fields of medical treatment, it is important to drain a body cavity of extraneous fluids in a sanitary and precisely controlled manner. For example, a common result of chest surgery and the puncturing of the chest wall or of organs therein, is the accumulation of blood, water, gas and other fluids in the pleural cavity. The accumulation of fluids or air in the pleural cavity can be very dangerous and even fatal. In such conditions, it is vitally important that means be provided for evacuating such fluids and air from the pleural cavity and for assisting the lung to its normal expansion or reexpansion. Essentially, this calls for the application of a level of suction on the pleural cavity to withdraw the extraneous fluids and air, and help re-inflate the lung once it has collapsed. For many years, a standard apparatus performing the evacuation process was an underwater seal drainage system known as the "3-bottle set-up". The 3-bottle set-up consists of a collection bottle, a water seal bottle and a suction control bottle. A catheter runs from the patient's pleural cavity to the collection bottle, and the suction bottle is connected by a tube to a suction source. The three bottles are connected in series by various tubes to apply a predetermined suction to the pleural cavity to withdraw fluid and air and discharge same into the collection bottle. Gases entering the collection bottle bubble through water in the water seal bottle. The water in the water seal also prevents the back flow of air into the chest cavity.
The 3-bottle set-up lost favor with the introduction of an underwater seal drainage system sold under the name "Pleur-evac" in 1966 by Deknatel Inc., the predecessor of the Deknatel Division of Howmedica Inc. U.S. Pat. Nos. 3,363,626; 3,363,627; 3,559,647; 3,683,913; 3,782,497; 4,258,824; and Re. 29,877 are directed to various aspects of the Pleur-evac system which has been marketed over the years. The Pleur-evac system provided improvements that eliminated various shortcomings of the 3-bottle set-up. These improvements have included the elimination of variations in the 3-bottle set-up that existed between different manufacturers, hospitals, and hospital laboratories, such variations including bottle size, tube length and diameter, stopper material and the like. Various inefficiencies and dangers have existed in the 3-bottle set-up resulting from the many separate components and the large number (usually 16 or 17) of connections, such as pneumothorax which may result from the loss of the water seal in the water seal bottle if suction were temporarily disconnected, and possible build-ups of positive pressure which could cause tension pneumothorax and possible mediastanal shift. Another serious shortcoming of the 3-bottle set-up is danger of incorrect connection and the time necessary to set the system up and to monitor its operation.
Among the features of the Pleur-evac system which provide its improved performance are employment of 3-bottle techniques in a single, pre-formed, self-contained unit. The desired values of suction are established by the levels of water in the suction control bottle and the water seal bottle, which levels are filled according to specified values prior to the application of the system to the patient. A special valve referred to as the "High Negativity Valve" is included which floats closed when the patient's negativity becomes sufficient to threaten loss of the water seal. Also, a "Positive Pressure Release Valve" in the large arm of the water seal chamber works to prevent a tension pneumothorax when pressure in the large arm of the water seal exceeds a prescribed value because of suction malfunction, accidental clamping or occlusion of the suction tube. The Pleur-evac system is disposable and helps in the battle to control cross-contamination.
Despite the advantages of the Pleur-evac system over the 3-bottle set-up and the general acceptance of the device in the medical community, there has remained a continuing need to improve the convenience and performance of chest drainage systems and to render such systems very compact. Underwater seal drainage systems as described above require the filling of manometer tubes to levels specified by the physician prior to being connected to the patient and the hospital suction system. Although it is conceivable that such filling could be performed at a manufacturing facility prior to shipment, as a practical matter this would not suffice because frequent adjustments are needed according to the different values of patient suction as dictated by the attending physician. Moreover, the presence of fluid in the various tubes could result in damage to the system during shipment such as because of freezing temperatures or because of leakage. In addition, accuracy of present underwater drainage systems is limited in that the filling of the manometers and the reading of the various gauges must be done visually by observing the liquid level in the respective chambers. A reduction in size of the system would offer such benefits as ease of use, ease of storage, less expensive shipping costs, and the reduction in the obstruction between the patient, his or her visitors and the medical staff.
Furthermore, the present underwater seal drainage systems are not conducive to incorporation in larger systems which perform other functions besides that of draining the pleural cavity and enabling the monitoring of a limited number of physical factors such as various pressure measurements. It would be a great advantage to have a drainage system which could be incorporated with other systems for the purpose of monitoring various important occurrences associated with the patient, such as temperature, respiration, pressure differentials, the quantity and flow rate of fluids drained from the patient and the like.
The use of electronic technology in conjunction with the monitoring of the drainage of body fluids is not entirely new. For instance, U.S. Pat. No. 4,206,727 describes a urological drainage monitor including an electronic timing system for periodically altering the liquid flow path into a series of receptacles for indicating the characteristics of fluid collected in each time period. However, systems for electronically controlling independent variables such as imposed suction and fluid flow and for electronically measuring the characteristics of gas flow and liquid flow associated with their drainage from the body was heretofore unknown.